Pressure accumulators are widely used in many types of hydraulic systems. One type of pressure accumulator comprises a thimble-shaped flexible bladder mounted in a generally cylindrical shaped rigid shell, the bladder serving to separate the interior of the shell into two separate compartments which are sealed from one another. A "liquid port" is provided at one end of the shell which communicates with one of the compartments, termed the "liquid compartment"; and a valved "gas port" is provided at the other end of the shell which communicates with the other compartment, termed the "gas compartment."
A compressible gas, such as nitrogen, is introduced through the gas port and is permanently charged and compressed under high pressure in the gas compartment of the accumulator. Then, an incompressible hydraulic liquid under high pressure is pumped through the liquid port into the liquid compartment. The flexible bladder is gradually forced into the gas compartment, as the liquid is pumped into the liquid compartment, thereby compressing the gas in the gas compartment until a balance high pressure is reached in both compartments. In this way, energy is stored or absorbed into the gas compartment of the accumulator, and this energy acts as a spring to force the incompressible hydraulic liquid out through the liquid port, thereby causing the hydraulic liquid to do useful work.
It is the usual practice to provide a spring-loaded poppet valve in the liquid port of the accumulator to prevent the bladder from extruding out of the liquid port after all the liquid has been discharged from the accumulator. Under normal operation, the poppet valve is held open by a spring, and is closed when the bladder engages the valve after all of the liquid has been expelled from the liquid compartment. The closure of the poppet valve prevents the gas pressure from forcing the bladder out through the liquid port.
It is highly desirable to provide an automatic safety device so that when the pressure in the accumulator reaches pressure well over the rated operating pressure of the accumulator, and below the rated burst pressure of the accumulator housing, the opening or mouth of the housing will deform outward, thus extruding the seal of the mouth and relieving the pressure built up in the accumulator. A successful method of accomplishing this is to insert the port and poppet assembly through an opening in the housing, and to seat this assembly on a segmented ring of larger diameter than the opening in the opening in the housing. This segmented ring has a beveled under surface which matches a beveled surface on the inside of the opening of the housing. The result is such that the port and poppet assembly protrude into the housing leaving sharp edges of the segmented ring which can cause damage to the bladder. Therefore, a filler grommet is utilized to cover the segmented ring.
Various types of retainers for the valve assembly have been suggested in the prior art. For example, Mercier U.S. Pat. No. 2,801,067 discloses one type of closure valve for the liquid port of a pressure accumulator which includes a tubular shell, and which is retained in the liquid port by means of a deformable locking ring which engages a shoulder on the valve housing, and which also engages the inner lip of the liquid port.
A subsequent Mercier U.S. Pat. No. 3,439,712 discloses another locking arrangement in which rigid arcuate segments of a retaining ring also engage the lip of the liquid port. The latter retaining ring includes a ring of resilient material which is bonded to the arcuate segments and which extends outwardly around the lip of the liquid port.
Yet another Mercier U.S. Pat. No. 3,148,705 discloses a locking assembly in which the segments of the retaining ring are shaped to extend into an annular recess in the resilient ring, so that the assembly may be held together without the necessity for bonding the resilient ring to the annular segments of the retaining ring. The assembly of the present invention is of the same general type described in this Mercier U.S. Pat. No. 3,148,705, and in the above-identified pending application, in that a resilient ring is held assembled to the arcuate segments of the retaining ring without bonding.